526 Forestry Quarterly 



basis of a rational increment management. "This stock would 

 naturally have to be frequently revised as regards determining its 

 productivity." Thus the normal stock is not any more a prede- 

 termined wood volimie, but a variable quantity. In place of a 

 dogma stands the experiment." 



He, then, discusses the application of the French mithode du 

 controle (see F. Q., xiii, pp. 43, 260). "This does not know a 

 normal stock which is supplanted by the more elastic principle 

 called etale, a conception which may be translated into stand 

 optimimi (rational stock)." This etale is that volume of stand 

 which is necessary and sufficient to continually produce the best 

 performance per acre. He conceives that the accumulation of 

 increments which make the stock leads finally to overfilling, a con- 

 dition impeding increment; hence when this occurs a felling is 

 indicated. The exact time for such is expressed by the behavior 

 of the current increment. The stand must also be so formed that 

 without damage according to silvicultural principles wood can be 

 taken out. This is done by selection until finally only the best 

 individuals remain to make the stand. Revisions in short periods 

 for every stand and the whole forest are necessary. 



This method allows the manager at any time when a detrimental 

 accumulation has arrived to reduce every single stand to the desir- 

 able amount of stock. No predetermined cycle, as in the normal 

 stock methods, troubles him, nothing absolute in its condition, 

 neither the stock per unit nor the percentic composition by diam- 

 eter classes, nor a determined maximum diameter. In building 

 up the "rational stock" regard must be had to silvicultural needs, 

 suiToimding physical, labor, and economic conditions, wood prices, 

 special needs, interest on capital, etc. 



How is sustained yield secured, he asks, when the sure foundation 

 of the normal forest is abandoned? What is yield? Is it not 

 increment ? As long as the basis for growth remains, yield is sus- 

 tained. If every stand, every acre is so managed as to produce 

 the maximtim increment, a careful and frequent determination of 

 the increment and of the condition of stands asstires the sustained 

 yield; more than that, an increased yield is secured through this 

 "rational stock." 



See Comment! 



Das Abnortne im Begriff " Nortnalvorrat." Schweizerische Zeitschrift fur 

 Forstwesen, March-April, 1916, pp. 53-67. 



